The Llantrisant and Taff Vale Junction Railway was a railway company that constructed a standard gauge line in South Wales, connecting Llantrisant and the Taff Vale Railway near Treforest. It ran through thinly populated country, and linked to a number of iron mines, collieries and other mineral sites. It opened in stages in 1863 and 1864. In 1865 through passenger trains from the Cowbridge Railway ran over the line, to Pontypridd, although for some time there were no passenger stations on its own network. At the Llantrisant end, it was reliant on broad gauge railway companies which were not always friendly to it. The company leased its line to the Taff Vale Railway in 1870.